1. Field of the Invention
The present invention relates to a clutch control system for use in an automatic transmission automobile.
2. Description of the Prior Art
There have been developed in recent years automatic transmission automobiles in which various mechanisms are controlled by an electronic control apparatus. In some such automatic transmission automobiles, a clutch control system is controlled by an electronic control apparatus. That is, a friction clutch, such as a dry-type single-disc clutch, is driven by a clutch actuator comprising a piston movable in a cylinder under hydraulic pressure, with the clutch actuator being controlled by the electronic control apparatus. One such system is described in Japanese Patent Application No. 58-119166 (Japanese Laid-Open Publication No. 60-11722), for example.
In such a clutch control system, the position of a partly connected clutch is learned by the electronic control apparatus and stored, and the position at which to start connecting the clutch (i.e., the position to start partly connecting the clutch) is automatically controlled on the basis of this learned value. According to the value learning process, the clutch is gradually connected from the condition in which the gear transmission is in the neutral position and the clutch is completely disconnected. The clutch position at a time T1 when the engine speed Ve and the speed of rotation Vi of an input shaft have reached certain values, is determined to be the position to start connecting the clutch, as shown in FIGS. 7 and 8.
With the clutch control system having such a learning capability, the viscosity of lubricating oil used to lubricate the gear transmission varies when the temperature of the lubricating oil changes with variations in the ambient temperature of the automobile. This results in an increase or a reduction in the drag torque of the gear transmission. As a consequence, the learned value of the position to start connecting the clutch is varied. If the automobile is started using the learned value, the engine tends to rev up before the clutch is partly connected, or the clutch may not be smoothly transferred to a partly connected condition.